1. Field of the Invention
The present invention relates to a resin molding method and a resin molding apparatus, and relates to, for example, a resin molding method and a resin molding apparatus that fill a space between a magnet hole provided in a rotor core of a motor and a magnet body inserted into the magnet hole with resin.
2. Description of Related Art
There is a technique of inserting a member to be fixed (e.g., magnet body) into an insertion hole provided in a workpiece and filling a space between the insertion hole and the member to be fixed with resin to fix the member to be fixed to the inside of the insertion hole. For example, a magnet hole is provided in a rotor core, which is a rotor of a motor, and a permanent magnet is inserted into the magnet hole. At this time, a gap between the magnet hole and the permanent magnet is filled with thermosetting resin to fix the permanent magnet to the inside of the magnet hole. One example of such a resin mold technique is disclosed in the specification of Japanese Patent No. 4865086.
In the method of manufacturing a laminated rotor core disclosed in the specification of Japanese Patent No. 4865086, an upper plate member and a lower plate member are arranged above and below the laminated rotor core, one of the upper plate member and the lower plate member including a resin pot that injects thermosetting resin into the magnet hole, the laminated rotor core is pushed by the upper plate member and the lower plate member from upper and lower sides, thermosetting resin that is melted in the resin pot is pushed out by a plunger, and the magnet hole is filled with thermosetting resin. Further, in the method of manufacturing the laminated rotor core disclosed in the specification of Japanese Patent No. 4865086, the resin pot is formed by its penetration through the upper plate member or the lower plate member where the resin pot is formed at a constant diameter.
In the method of manufacturing the laminated rotor core disclosed in the specification of Japanese Patent No. 4865086, the upper plate member and the lower plate member including the resin pot that substantially close the magnet hole are provided above and below the laminated rotor core. Therefore, when resin is injected into the magnet hole, molten resin discharged from the resin pot enters the magnet hole and is thermally cured, whereby the permanent magnet arranged inside can be fixed to the inside of the magnet hole.
In the technique disclosed in the specification of Japanese Patent No. 4865086, thermosetting resin in the resin pot is pushed out by the plunger to fill the magnet hole with thermosetting resin. The magnet hole starts to be filled with thermosetting resin in a state in which thermosetting resin is heated to an even temperature in the pot. Further, thermosetting resin starts to be cured due to a heat in the magnet hole and the resin pot when it is injected into the magnet hole. Therefore, in the stage in which thermosetting resin which is in a side of the pot far from the workpiece (or a side of the pot close to the plunger) is injected into the magnet hole, the viscosity of thermosetting resin injected into the magnet hole becomes high. Therefore, when the magnet hole is filled with thermosetting resin using the technique disclosed in the specification of Japanese Patent No. 4865086, the magnet hole may not be sufficiently filled with thermosetting resin. A part of the magnet hole having a gap between it and the magnet which is relatively large tends to be filled first with molten resin. There is also a narrow space between the magnet hole and the magnet. Since this narrow space is filled with thermosetting resin at the last stage of the filling process, when the viscosity of molten resin that enters the magnet hole at the last stage is high, hardly any molten resin enters the narrow space.
The present invention has been made in view of the above circumstances and aims to sufficiently fill a narrow space with thermosetting resin.